Long Term Evolution (LTE) Advanced is a mobile telecommunication standard proposed by the 3rd Generation Partnership Project (3GPP) and first standardised in 3GPP Release 10. In order to provide the peak bandwidth requirements of a 4th Generation system as defined by the International Telecommunication Union Radiocommunication (ITU-R) Sector, while maintaining compatibility with legacy mobile communication equipment, LTE Advanced proposes the aggregation of multiple carrier signals (carrier components) in order to provide a higher aggregate bandwidth than would be available if transmitting via a single carrier signal. This technique of Carrier Aggregation (CA) requires each utilised carrier signal, that is to say radio frequency signal, to be demodulated in a receiver at a wireless communications terminal, whereafter the message data from each of the signals can be combined in order to reconstruct the original data. Carrier Aggregation can be used also in other radio communication protocols such as High Speed Packet Access (HSPA).
Carrier Aggregation may involve aggregation of radio frequency signals that are transmitted in the same frequency band, or aggregation of radio frequency signals that are transmitted in different frequency bands. A frequency band may be a range of radio frequencies allocated to an operator as a contiguous block, or part of a contiguous block, and typically a radio receiver for receiving a radio frequency signal will have a front end band pass filter arranged to encompass the frequency band, but reject signals transmitted in other bands and/or out of band. The front end filter serves to protect the receiver from saturation, blocking and interference by out of band signals, which may be at a high power level and beyond the operator's control.
If data is transmitted using carrier aggregation of radio frequency signals that are transmitted in the same frequency band, a single band pass filter may be used to receive the carrier aggregated signals, and a receiver chain for each of the radio frequency signals may be arranged to receive signals that have passed through the hand pass filter. However, if data is transmitted using carrier aggregation of radio frequency signals that are transmitted in different frequency bands, more than one band pass filter is typically required to receive the carrier aggregated signals, and each receiver chain typically needs to be arranged to receive signals that have passed through the appropriate band pass filter.
A radio receiver may also be required to be configured for use in multi-SIM (Subscriber Information Module) operation, in which data or paging signals may be received using several carriers, each carrier typically relating to a SIM or USIM (Universal Subscriber Information Module), the carriers being in either the same or different operating frequency bands.
A wireless communications terminal may be required to be reconfigurable between a configuration for receiving data that is transmitted using carrier aggregation or multi-SIM operation of radio frequency signals in the same band, and a configuration for receiving data that is transmitted using carrier aggregation or multi-SIM operation of radio frequency signals in different bands. A reconfigurable radio frequency circuit is required for use in such a wireless communications terminal, to allow appropriately filtered signal paths having required radio frequency performance to be configured between one or more antennas and receive chains used to receive respective radio frequency signals, which may have been transmitted in the same or different frequency bands.